High vacuum chambers capable of pressures in the 10.sup. .sup.-8 torr and lower range are now widely used, for example, in solid state electronic research. These chambers are usually made of stainless steel so that they will not oxidize when exposed to gases and vapors normally used in solid state work or when bake-out procedures at several hundred degrees are conducted. Vacuum pumps, gas generators and other peripheral devices are regularly connected and disconnected to ports on the chambers by means of bolted flanged couplings and sealing gaskets. The most effective seals have been used between two stainless steel couplings. The couplings are provided with knife edges and these bite into the gasket which is usually a washer of very pure copper alloy.
Occasionally it is necessary to couple a device, perhaps from another vacuum system, which is made of a different metal, e.g. aluminum. The resulting galvanic action between a metal gasket and the different metals on either side can easily result in contamination of a sample under study in the chamber, damage to the chamber or loss of vacuum. To prevent this some systems have been provided with grooved flanges and organic O-rings. Organic materials normally disintegrate at bake out temperature or give off gases that contaminate pure crystalline samples. The use of such O-rings is still further limited where multiple interconnections are involved due to the mechanical and chemical interactions which occur at operating temperatures. An object of the invention, therefore, is to provide a seal as reliable as those used in all stainless steel systems, by using metals mechanically and galvanically compatible with the particular system involved.